A mass-balancing device of the type named above is already known from JP 60109639 A and JP 60109636 A. The transmissions disclosed there have two intermeshing spur gears that are provided with elliptical and identical rolling circles for generating the non-uniform transmission ratio and that rotate about eccentric axes each with respect to the center point of the ellipse.
In JP 58225242 A and JP 58225243 A, mass-balancing devices for single-cylinder internal combustion engines are disclosed that have transmissions that also have two identical, intermeshing, elliptical spur gears. The mass-balancing devices are each configured, however, so that the angular speed of the balancer shafts is at a maximum at the piston top dead center and is at a minimum at the piston bottom dead center.
DE 10 2004 033 927 A1 discloses a mass-balancing device with a transmission constructed as a chain drive or toothed-belt drive. There it is proposed for the driving wheel of the crankshaft and/or the driving wheels of the balancer shafts to have a non-round construction, in order to impart, on the drive, a non-uniform characteristic that compensates for the rotational fluctuations of the crankshaft.